Thank you for the information. So this lock is a model 217. The patent, which dates to 1968, is for a hardened steel body padlock. But the mechanism is probably similar to the brass padlock if not identical. I tend to assume the brass version predates the steel version. The patent refers to an older patent, from 1935, US 2,070,012 which describes a somewhat similar padlock.
I also have one of the model 221 padlocks which I cut open and created a brass key. I also have a contemporary equivalent which is now called the 3020. (stock image)
